Low creep high strength ferrous alloy

ABSTRACT

A new alloy is provided having low creep and high strength at elevated temperatures which is resistant to corrosion and thermal shock and has unusual stress rupture characteristics at elevated temperatures comprising about 0.3% to 0.9% carbon, about 20% to 30% chromium, about 15% to 35% nickel, about 0.8% to 4% manganese, about 0.9% to 3.5% silicon, about 0.3% to 5% tungsten, about 0.03% to 0.15% sulfur and the balance iron with residual impurities in ordinary amounts.

United States Patent English Dec. 24, 1974 LOW CREEP HIGH STRENGTHFERROUS 3,165,400 l/l965 Roy 75/128 A ALLOY 3,260,594 7/1966 Ornitz75/1211 A 3,376,780 4/1968 Tanczyn 75/l28 P Inventor: y g McCandless3,563,729 2/1071 Kovach H 75/1211 P Township, Allegheny County, Pa. [73]Assignee: Blair-Knox Company, Pittsburgh, Primary B1101 p Attorney,Agent, or FirmBuell, Blenko and Ziesenheim [22] F1led: Feb. 12, 1970[21] Appl. No: 11,001 [57] ABSTRACT A new alloy is provided having lowcreep and high [5 US Cl- 5/1 8 A, 75/128 P strength at elevatedtemperatures which is resistant to [51] Int. Cl. C22c 39/20 corrosionand thermal shock and has unusual stress [58] Field of Search 75/128 A,128 W, 128 P rupture characteristics at elevated temperatures comprisingabout 0.3% to 0.9% carbon, about to [56] References Cited chromium,about 15% to nickel, about 0.8% to UNITED STATES PATENTS 4% manganese,about 0.9% to 3.5% silicon, about 2557 862 6/1951 Clarke /128 P 0.3% to5% tungsten, about 0.03% to 0.15% sulfur 2:677:610 5/1954 75/128 P andthe balance iron with residual impurities in ordi- 2,686,116 8/1954Schempp 75/128 F y amounts- Tanczyn 75/128 W 3 Claims, No DrawingsBalass .1 75/128 W 7 LOW CREEP HIGH STRENGTH FERROUS ALLOY Thisinvention relates to high temperature alloys and particularly to analloy and parts made therefrom having high strength and low creep in thetemperature range l,600 to 2,200F. coupled with resistance to corrosionand thermal shock. The need for alloys having high strength and lowcreep, coupled with resistance to corrosion and thermal shock in thetemperature range of 2,000 F., has long been recognized. Conventionalalloys used for applications in this temperature range have not beensatisfactory for most uses because of the high rate of creep, corrosionand lack of strength at temperatures at or about 1,600 to 2,200 F.

l have discovered an alloy composition having high strength and lowcreep characteristics coupled with corrosion resistance and highresistance to thermal shock at temperatures of about l,600 to 2,200 P.The surprising characteristics of this alloy appear to be particularlydependent upon the control of carbon, manganese, tungsten and sulfurwithin a critical nickelchromium iron base analysis. The broadcomposition range of the alloy of this invention lies within thefollowing limits:

Sulfur about 0.030 to about 0.15% Carbon about 0.3% to about 0.9%Chromium about 17% to about 30% Nickel about to about 35% Manganeseabout 0.8% to about 4% Silicon about 0.9% to about 3.5% Tungsten about0.3% to about 5 Balance iron with residual impurities in ordinaryamounts While the foregoing broad alloy composition will give generallysatisfactory results at or above 1,800 F., I have found that forcontinued service above about 2,100 F. the following narrower range ofcomposition should be observed:

Sulfur about 0.035 to about 0.100% Carbon about 0.35% to about 0.75%Chromium about 20% to about 30% Nickel about 30% to about 35% Manganeseabout 1.2% to about 2.4% Silicon about 1.2% to about 2.5% Tungsten about1.75% to about 5% Balance iron with residual impurities in ordinaryamounts A single preferred composition would be:

Sulfur about 0.075%

Carbon about 0.4%

Chromium about 23% Nickel about 30% Manganese about 1.5%

Silicon about 2% Tungsten about 1.75%

Balance iron with residual impurities in ordinary amounts This inventionis surprising in that the high sulfur in the present alloy compositionappears to act precisely contrary to what would be expected. It has longbeen recognized that the presence of sulfur above about 0.025% in steelsor iron based alloys would cause red shortness and the strength andresistance to cracking at high temperatures, particularly when worked orloaded, was drastically reduced. In the present alloy, on

EXAMPLE Two alloys were melted having the following compo sitions:

Alloy C Mn Si Ni Cr W S Bal Alloy 1 Fe usual impurities Alloy 11 Feusual impurities Alloy l is a recognized high temperature alloy havingextraordinary stress rupture characteristics as compared with mostalloys. It is sold by Blaw-Knox Company under the trade mark Mo Re No. 1for high temperature and high stress application.

Alloy 11 is a composition according to the present invention.

These two alloys were formed into identical test pieces and subjected tostress rupture tests at 1,900" P. and 3,400 lbs. of stress underidentical conditions.

The test piece formed from Alloy No. 1 developed hours of life. I

The test piece formed from Alloy No. 2 developed 883 hours of life, oralmost 9 times the life of the best alloy heretofore available for hightemperature high stress applications. This is a very surprising result.

The reason for this surprising result is not known to me. I believe,however, that it is the result of a redistribution of carbides in thematrix due to the presence of the sulfur in this particular alloycomposition. It may,

of course, be the result of the formation of a complex sulfur metalcarbide composition. Whatever the mechanism, it is most unique andsurprising result.

While I have described certain preferred embodiments of my invention inthe foregoing specification, it will be understood that the inventionmay be otherwise embodied with the scope of the following claims.

1 claim:

1. A low creep, high strength alloy resistant to corro sion and thermalshock at elevated temperatures and having unusual stress rupturecharacteristics at elevated temperatures consisting essentially of about0.3% to 0.9% carbon, about 20% to 30% chromium, about to 35% nickel,about 0.8% to 4% manganese, about 0.9% to 3.5% silicon, about 0.3% to 5%tungsten, about 0.030% to about 0.15% sulfur and the balance iron withresidual impurities in ordinary amounts.

2. A low creep, high strength alloy resistant to corrosion and thermalshock at elevated temperatures having unusual stress rupturecharacteristics at elevated temperatures consisting essentially of about0.35% to 0.75% carbon, about 20% to 30% chromium, about 30% to 35%nickel, about 1.2% "to 2.4% manganese, about 1.2% to 2.5% silicon, about1.75%% to 5% tungsten, about 0.035% to 0.10% sulfur and the balance ironwith residual impurities in ordinary amounts.

3. A low creep, high stre gth alloy resistant to corro- I manganese,about 2% siliim, about 1.75% tungsten, sion and thermal shock attemperatures of 1,600 to about 0.075% sulfur and the balance iron withresidual 2,200 F. consisting essentially of about 0.4% carbon,impurities in ordinary amounts. about 23% chromium, about 30% nickel,about 1.5% 5

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patmn:No.3 85 5ImtedDecpmber 24, 1974 Invmmorkfi Ray H. English It is certified thaterror appears in the above-identified patent and that said LettersPatent'are hereby corrected as shown below:

The name of the Assignee should read:

"BLAW-KNOX COMPANY" Column 2, line 65, "l.75%%" should read l.75%.

Signed and sealed this 4th day of March 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officerand Trademarks usco'MM-Dc 60376 P69 1* I145. GOVERNMENT PRINTNG OFFICEI!" 0-3'6-3 l.

F ORM PO-\ 050 (10-69)

1. A LOW CREEP, HIGH STRENGTH ALLOY RESISTANT TO CORROSION AND THERMALSHOCK AT ELEVATED TEMPERATURES AND HAVING UNUSUAL STRESS REPTURECHARACTERISTICS AT ELEVATED TEMPERATURES CONSISTING ESSENTIALLY OF ABOUT0.3% TO 0.9% CARBON, ABOUT 20% TO 30% CHROMIUM, ABOUT 15% TO 35% NICKEL,ABOUT 0.8% TO 4% MANGANESE, ABOUT 0.9% TO 3.5% SILICON, ABOUT 0.3% TO 5%TUNGSTEN, ABOUT 0.030% TO ABOUT 0.15% SULFUR AND THE BALANCE IRON WITHRESIDUAL IMPURITIES IN ORDINARY AMOUNTS.
 2. A low creep, high strengthalloy resistant to corrosion and thermal shock at elevated temperatureshaving unusual stress rupture characteristics at elevated temperaturesconsisting essentially of about 0.35% to 0.75% carbon, about 20% to 30%chromium, about 30% to 35% nickel, about 1.2% to 2.4% manganese, about1.2% to 2.5% silicon, about 1.75%% to 5% tungsten, about 0.035% to 0.10%sulfur and the balance iron with residual impurities in ordinaryamounts.
 3. A low creep, high strength alloy resistant to corrosion andthermal shock at temperatures of 1,600* to 2,200* F. consistingessentially of about 0.4% carbon, about 23% chromium, about 30% nickel,about 1.5% manganese, about 2% silicon, about 1.75% tungsten, about0.075% sulfur and the balance iron with residual impurities in ordinaryamounts.